"This forward-bias voltage drop exhibited by the diode is due to the action of the depletion region formed by the P-N junction under the influence of an applied voltage. If no voltage applied is across a semiconductor diode, a thin depletion region exists around the region of the P-N junction, preventing current flow."

The sentence: "If no voltage applied is across a semiconductor diode, a thin depletion region exists around the region of the P-N junction, preventing current flow." Should be corrected as follow:

If no voltage is applied across a semiconductor diode, a thin depletion region exists around the region of the P-N junction, preventing current flow."

And then separated from the paragraph and moved above the following sentence as an independent sentence:

"If a reverse-biasing voltage is applied across the P-N junction, this depletion region expands, further resisting any current through it."

This change makes the thought transition smooth and understandable to the reader.

A forward-biased diode conducts current and drops a small voltage across it, leaving most of the battery voltage dropped across the lamp. If the battery's polarity is reversed, the diode becomes reverse-biased, and drops all of the battery's voltage leaving none for the lamp. If we consider the diode to be a self-actuating switch (closed in the forward-bias mode and open in the reverse-bias mode), this behavior makes sense. The most substantial difference is that the diode drops a lot more voltage when conducting than the average mechanical switch (0.7 volts versus tens of millivolts).

This forward-bias voltage drop exhibited by the diode is due to the action of the depletion region formed by the P-N junction under the influence of an applied voltage. If no voltage applied is across a semiconductor diode, a thin depletion region exists around the region of the P-N junction, preventing current flow. (Figure below (a)) The depletion region is almost devoid of available charge carriers, and acts as an insulator:

The schematic symbol of the diode is shown in Figure above (b) such that the anode (pointing end) corresponds to the P-type semiconductor at (a). The cathode bar, non-pointing end, at (b) corresponds to the N-type material at (a). Also note that the cathode stripe on the physical part (c) corresponds to the cathode on the symbol.

If a reverse-biasing voltage is applied across the P-N junction, this depletion region expands, further resisting any current through it. (Figure below)

Depletion region expands with reverse bias.

Conversely, if a forward-biasing voltage is applied across the P-N junction, the depletion region collapses becoming thinner. The diode becomes less resistive to current through it. In order for a sustained current to go through the diode; though, the depletion region must be fully collapsed by the applied voltage. This takes a certain minimum voltage to accomplish, called the forward voltage as illustrated in Figure below.

For silicon diodes, the typical forward voltage is 0.7 volts, nominal. For germanium diodes, the forward voltage is only 0.3 volts. The chemical constituency of the P-N junction comprising the diode accounts for its nominal forward voltage figure, which is why silicon and germanium diodes have such different forward voltages. Forward voltage drop remains approximately constant for a wide range of diode currents, meaning that diode voltage drop is not like that of a resistor or even a normal (closed) switch. For most simplified circuit analysis, the voltage drop across a conducting diode may be considered constant at the nominal figure and not related to the amount of current.

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This strikes me as a context issue. The section by itself would need additional information, but if you read the section in context there is a full and complete explanation given.

Your input is important. I think you need to step back and see if what you are saying has been addressed within a couple of sentences, as in this case. A paragraph exists as part of a larger whole.

I agree with you bill that this section provides the necessary information. However, the sentence structure needs to be corrected "is" before "applied" vs "is" after "applied" and the whole sentence should be moved as indicated in my previous post, if you want the reader to get a better understanding of the concept.

All in all there are a lot of good information in this section for the reader.

If you go through my previous corrections you will note I do a before and after sentence, it prevents confusion and points out where you are referring to. The quote feature is very useful for this, although I find I have to clean up the text linefeeds sometimes to make it match. A single sentence is extremely hard to find, I usually try to include an illustration for reference.

Minor text corrections are always appreciated. You need to be very clear what you need corrected though.